(Not including over 50 seminar talks or invited lectures in more than 40 foreign universities of research institutes in Asia, Europe and North America)

I = invited talk

R = accepted by an international program committee

- "Interactive L-systems with almost interactionless behaviour" (with K. Culik II) in "8th International Symposium on Mathematical Foundations of Computer Science", Olomouc, Czechoslovakia, September 1979, R.
- "Generalized Parikh mappings and homomorphisms" in "8th International Colloquium on Automata, Languages and Programming", Acre (Akko), Israel, July 1981, R.
- "On strongly cube-free w-words generated by binary morphisms" in "International Conference on Fundamentals of Computation Theory", Szeged, Hungary, August 1981, R.
- "Marked morphisms: a tool for solving problems concerning morphisms over a binary alphabet" in Conference "Fete des Mots", Rouen, France, June 1982, I.
- "On the equivalence problem for binary DOL systems" in "9th International Colloquium on Automata, Languages and Programming", Aarhus, Denmark, July 1982, R.
- "On test sets and the Ehrenfeucht conjecture" (with K. Culik II) in "9th International Colloquium on Automata, Languages and Programming", Aarhus, Denmark, July 1982, R.
- "Marked morphisms: A tool for solving problems concerning morphisms over a binary alphabet" in "2nd Conference on Foundations of Software Technology and Theoretical Computer Science", Bengalore, India, December 1982, R.
- "Test sets for bounded delay morphisms" (with C. Choffrut) in "10th International Colloquium on Automata, Languages and Programming", Barcelona, Spain, July 1983, R.
- "A note on the intersection of free submonoids of a free monoid" in "10th International Colloquium on Automata, Languages and Programming", Barcelona, Spain, July 1983, R.
- "A property of three-element codes" in "Symposium on Theoretical Aspects of Computer Science", Paris, France, April 1984, R.
- "On three-element codes" in "11th International Colloquium on Automata, Languages and Programming 84", Antwerp, Belgium, July 1984, R.
- "On equivalence of morphisms and inverse morphisms on regular language" (with H.C.M. Kleijn) in "11th International Symposium on Mathematical Foundations on Computer Science", Praha, Czechoslovakia, September 1984, R.
- "The equivalence of finite valued transducers is decidable" (with K. Culik II) in "12th International Symposium on Mathematical Foundations of Computer Science", Bratislava, Czechoslovakia, August 1986, R.
- "Equivalence of mappings on languages" in "4th International Meeting of Young Computer Scientists", Smolenice Castle, Czechoslovakia, October 1986, I.
- "On recent trends in formal language theory in "14th International Colloquium on Automata, Languages and Programming", Karlsruhe, Germany, July 1987, I.
- "Morphisms of free monoids: A source of challenging problems" in "20th Nordic Congress of Mathematicians", Trondheim, Norway, August 1988, I.
- "On the Equivalence Problem for Deterministic Multitape Automata and Transducers" (with K. Culik II) in "6th Annual Symposium on Theoretical Aspects of Computer Science", Paderborn, Germany, February 1989, R.
- "On the equivalence of multitape deterministic finite automata" (with K. Culik II) in congress "Fundamentals of Computation Theory",Szeged, Hungary, August 1989, I.
- "On the power of synchronization in parallel computations" (with J. Dassow, J. Hromkovic, B. Rovan and A. Slobodova), Porabka, Poland, August, 1989, R.
- "Decidability of the multiplicity equivalence of finite multitape automata" (with T. Harju) in "22nd Annual ACM Symposium on Theory of Computing", Baltimore, Maryland, May 1990, R.
- "The equivalence problem of multitape finite automata" (with T. Harju) in "International Congress of Mathematicians", Kyoto, Japan, August 1990, I.
- "Systems of equations over finite sets of words and automata theory" in "International Colloquium on Words, Languages and Combinatorics", Kyoto, Japan, August 1990, I.
- "The equivalence problem for deterministic multitape automata" in Toyhashi Symposium on Theoretical Computer Science", Toyohashi, Japan, August 1990, I.
- "Use of algebra in solving equivalence problems in automata theory" in "Workshop on Algebraic Code Theory and Related Topics", Kyoto, Japan, September 1990, I.
- "Use of algebra in solving equivalence problems in automata theory" in "4th Congress of Vietnamese Mathematicians", Hanoi, Vietnam, September 1990, I.
- "Efficient constructions of test sets for regular and context-free languages" in Dagsthul Meeting on "Automata Theory and Applications in Logic and Complexity", Dagsthul, Germany, January 1991, I.
- "Efficient constructions of test sets for regular and context-free languages" (with S. Jarominek and W. Rytter) in "16th International Symposium on Mathematical Foundations of Computer Science", Warsaw, Poland, September 1991, R.
- "Finite automata computing real functions" in Dagstuhl Meeting on "Automata Theory: Infinite Computations", Dagstuhl, Germany, January 1992, I.
- "Iterative devices generating infinite words" (with K. Culik II) in "9th Symposium on Theoretical Aspects of Computer Science", Paris, France, February 1992, R.
- "Polynomial size test set for context-free languages" (with W. Plandowski and W. Rytter) in "19th International Colloquium on Automata, Languages and Programming", Vienna, Austria, July 1992, R.
- "On computational power of weighted finite automata" (with D. Derencourt, M. Latteux and A. Terlutte) in "17th International Symposium on Mathematical Foundations of Computer Science", Prague, Czechoslovakia, August 1992, R.
- "On the size of independent systems of equations in semigroups " (with W. Plandowski) in "19th International Symposium on Mathematical Foundations of Computer Science", Kosice, Slovakia, August 1994, R.
- "Two lower bounds on complexity of infinite word generation" (with J. Hromkovic) in "13th World Computer Conference", Hamburg, Germany, August 1994, R.
- "Toeplitz words, generalized periodicity and periodically iterated morphisms" (with J. Cassaigne) in "First Annual International Conference Combinatorics and Computing", Xian, China, August 1995, R.
- "Compactness of Systems of Equations in Semigroups" (with T. Harju and W. Plandowski) in "22nd International Colloquium on Automata, Languages and Programming", Szeged, Hungary, July 1995, R.
- "Remarks on Generalized Post Correspondence Problem (with T. Harju and D. Krob) in "13th Symposium on Theoretical Aspects of Computer science", Grenoble, France, February 1996, R.
- "On expressibility of languages and relations by word equations" (with F. Mignosi and W. Plandowski) in "24th International Colloquium on Automata, Languages and Programming", Bologna, Italy, July 1997, R.
- "A lower bound for a constant in Shallit's Conjecture" (with F. Mignosi and W. Plandowski) in "3rd Conference on Developments in Language Theory", Thessaloniki, Greece, July 1997, R.
- "Pattern-matching problems for 2-dimensional images described by finite automata" (with W. Plandowski and W. Rytter) in "11th International Symposium on Fundamentals of Computing Theory", Krakow, Poland, September, 1997, R.
- "Problems on F-presentations of semigroups" in Conference on Words, Rouen, France, September 1997, I.
- "Locally periodic infinite words and chaotic behaviour" (with A. Lepistö and W. Plandowski) in "25th International Colloquium on Automata, Languages and Programming", Aalberg, Denmark, July 1998, R.
- "On defect effect of bi-infinite words" (with J. Manuch and W. Plandowski) in "23rd Internatinoal Symposium on Mathematical Foundations of Computer Science", Brno, Czech's Republic, August 1998, R.
- "On the power of word equations", in "Fourth International Conference Developments in Language Theory", Aachen, Germany, July, 1999, I.
- "Defect theorems for trees" (with S. Mantaci), in "Fourth international Conference Developments in Language Theory", Aachen, Germany, July 1999, R.
- "On the complexity of computing the order of repetition in a string" (with W. Plandowski and W. Rytter), in "Fourth international Conference Developments in Language Theory", Aachen, Germany, July 1999, R.
- "The compression of subsegments of images described by finite automata" (with W. Plandowski and W. Rytter) in "10th annual Conference om combinatorial Pattern Matching", Warwick, July 1999, R.
- "The equivalence problem for different variants of finite transducers", in "9th Conference on Automata and Formal Languages", Hungary, August, 1999, I.
- "Characterizing subsets of words commuting with a two-element set" (with C. Choffrut), in "Seventh Nordic Combinatorial Conference", Turku, August, 1999, I.
- "The commutation of finite sets: a challenging problem", in "Second conference of Words", Rouen, September, 1999, I.
- "Many aspects of defect theorems", in "1st South Asian Conference on Mathematical Foundations of Informatics, MFI-Hanoi 99", Hanoi, Vietnam, October, 1999, I.
- "On expressibility of languages by word equations with a bounded number of variables" (with F. Mignosi and W. Plandowski), in 8enoes Journees Montoises d'Infomatique Theorique, Paris, France, March 2000, R.
- "Remarks on language equations", in "4th International Colloquium on Words, Languages and Combinatorics", Kyoto, Japan, March, 2000, I.
- "Some open problems on combinatorics of words", in Workshop on Discrete Systems and Formal Languages, Kyoto, Japan, March 2000, I.
- "On the centralizer of finite languages" (with I. Petre), in "27th International Colloquium on Automata, Languages and Programming", Geneva, July, 2000, R.
- "Measures of nondeterminism in finite automata" (with J. Hromkovic, H. Klauck, G. Schnitger, and S. Seibert), in "27th International Colloquium on Automata, Languages and Programming", Geneva, July, 2000, R.
- "A simple undecidable problem: The inclusion problem for finite substitutions on ab*c", in "18th Symposium on Theoretical Aspects of Computer Science", Dresden, February, 2001, R.
- "Combinatorial and Computational problems on finite sets of words", in "International Conference on Universal Machines and Computations", Moldavia, 2001, I.
- "Decision questions concerning semilinearity, morphisms and commutation of languages" (with T. Harju, O. Ibarra and A. Salomaa), in "28th International Colloquium on Automata, Languages and Programming", Crete, July, 2001, R.
- "A note on Synchronized automata and road coloring problem", in "5th International Conference on Developments in Language Theory", Vienna, July, 2001, R.
- "A fixed point approach to the commutation of languages", Workshop on Automata and Languages, Szeged, July 2001, I.
- "Challenges of commutation: an advertisement", in "13th International Symposium on Fundamentals of Computing Theory", Riga, August, 2001, I.
- "Challenging problems on finite sets of words", 100 year anniversary conference in honor of P.S. Novikov, Moscow, August, 2001, I.
- "From words to finite sets of words", WORDS 2001, Palermo, September, 2001, I.
- "From words to finite sets of words", German Theory Day, Magdeburg, October, 2001, I.
- Kutsuttu pääesitelmä, Suomen matemaatikkopäivät, Joensuu 2002, I.
- "Finite automata and image compression", Weighted Automata: Theory and practice, Dresden, March 2002, I.
- "Combinatorics on words: a new challenging topic", Finest 02, Tallinn, Estonia, May 2002, I
- "Applications of finite automata" in "26th International Symposioum on Mathematical Foundations of Computer Science", Warsaw, Poland, August, 2002, I.
- "The equivalence problem of finite substitutions on ab*c, with applications", in "29th International Colloquium on Automata, Languages and Programming", Malaga, Spain, July 2002 (with L. Lisovik), R.
- "Computing Partial Information out or Intractable One - The First Digit of 2^n at Base 3 as an Example", 25th international Symposium on Mathematical Foundations of Computer Science, Warsaw, Poland, August 2002 (with M. Hirvensalo), R
- "(G)PCP for words of length two", "9eme Journées Montoises", Montpellier, France, September 2002 (with V. Halava, T.Harju and M. Hirvensalo), R
- "Decidability questions on finite sets of words" Computer Science: from Theory to Practice (a workshop in honour of Oscar Ibarra's 60th birthday), Singapore, August 2002, I
- "The commutation with codes and ternary sets of words", 20th Symposium on Theoretical Aspects of Computer Science, Berlin, February, 2003, R
- Automata on words, in 8th International Conference on Implementation and Application of Automata, Santa Barbara, California, July 2003.
- "On some special equations on words", Dixièmes Journées Montoises d'Informatique Théoretique, Liege, Belgium, September, 2004 (with E. Petre), R
- "Finite sets of words and computing", 4th International Conference Machines, Computations and Universality, St. Petersburg, Russia, September, 2004, I
- "Combinatorics on words and complexity", Conference on Automata and Formal Languages, Hungary, May, 2005, I
- "Computing by commuting", A satellite event for ICALP, Lisbon, Portugal, July, 2005 (with A. Okhotin and M. Kunc), R
- "Post Correspondence Problem for morphisms with unique blocks", Conference on WORDS, Montreal, Canada, September, 2005 (with V. Halava, T. Harju and M. Latteux), R
- "Open problems and exercises on words and languages", Conference on Algebraic Informatics, Thessaloniki, Greece, October, 2005, I
- "Words vs. matrices", A tutorial lecture in EMS International Summer School and Conference on Combinatorics, Automata and Number Theory, Liege, Belgium, May, 2006, I (6 hours)
- "Communication of two stacks and rewriting", International Colloquium on Automata, Languages and Programming, Venice, Italy, July, 2006 (with A. Okhotin and M. Kunc), R
- "Dimension properties of words", International Conference: Leonhard Euler and Modern Combinatorics, Russian Academy of Sciences, St. Petersburg Department of Steklov Mathematical Institute and Euler International Mathematical Institute, St. Petersburg, Russia, June, 2007, I
- "Conjugacy of finite biprefix codes", Workshop on Theory and Application of Language Equations, Turku, Finland, July, 2007 (with J. Cassaigne and P. Salmela), R
- "Tiling periodicity", Conference on Combinatorial Pattern Matching, London, Canada, July, 2007 (with Y. Lifshits and W. Rytter), R
- "Connections between matrices and words", Shanghai Conference on Combinatorics, Shanghai, China, May, 2008, I
- "Dimension properties of words", 6 tutorial lectures in graduate school at Jiao Tong University, Shanghai, China, May, 2008, I
- "Reachability via Cooperating Morphisms", Workshop on Reachability Problems, Liverpool, England, September, 2008 invited
- "An analysis and a reproof of Hmelevskii's theorem", 12th International conference on Developments in Language Theorey, Kyoto, Japan, September 2008 (with A. Saarela), R
- "Noneffective regularity of equality languages and bounded delay morphisms", Auto Math A conference, ESF, University of Liege, Belgium, June 2009 (with A. Saarela), R
- "Unique decipherability in the monoid of languages: an application of rational relations", 4th International computer science symposium in Russia, Novosibirsk, Russia, August 2009 (with C. Choffrut), R
- "To be announced", 10th Nordic Combinatorial Conference, Reykjavik, Iceland, May 2010, I.